There are known difficulties that a dentist encounters in order to make the matrix adhere perfectly to the tooth during filling, particularly the back teeth, when the tooth exhibits in an approximal zone an indentation, in other words the so-called "radicular recess."
Presently transparent matrices are largely used when the filling is done with a resin that can be hardened by illumination. The matrix is normally held in place by a wedge, also transparent, which is illuminated so as to refract the light rays onto the matrix and thereby onto the filling.
However the wedge is incapable of making the matrix adhere perfectly to the tooth when the tooth exhibits an indentation, in other words a radicular recess. This deficiency generally results in an excess of filling material at the approximal cervical level, from where it can be removed only with great difficulty.